In health service as well as medical service it is common to take specimens of body fluids or tissue and then analyze the specimens under a microscope or by applying some other optical method. To render the analysis possible, the specimens taken must usually be placed on or in some testing device, such as on a glass slide or in a cuvette.
One example of that stated above is so-called differential calculus of white corpuscles, in which the relative distribution of white corpuscles between five main classes of white corpuscles is determined so as to obtain an indication of various states of ill-health.
Traditionally, differential calculus is carried out completely manually. A blood sample is taken from a patient whose blood is to be analyzed. A few drops of the sample are dripped onto a glass slide and are smeared as a thin layer over the surface of the slide by means of an inclined smaller glass slide. Subsequently, the blood is fixed and colored on the slide. Finally, the slide is placed in a microscope, and the blood is studied by a laboratory technician who counts the white blood corpuscles in a suitable area on the slide and determines to which main class each of these belongs.
The manual differential calculus is time-consuming and not very rational. Attempts have therefore been made to automate it in various ways.
For instance, it is known to smear the blood on the slide by means of a spinner. The empty slide is placed manually in a holder in the spinner, whereupon a few drops of blood are dripped onto the slide which is spun, thereby distributing the blood as a thin layer over the slide surface. Then the slide is removed manually from the spinner.
A difficulty in connection with the spinning operation is how the surplus blood, i.e. the blood which during spinning is moved away from the surface of the slide, should be taken care of. Part of the blood is aerosolized at the sharp edge of the slide and settles in various positions inside the spinner, while part of the blood flows over the edge of the slide and gets stuck in the slide holder. Since the handling of blood means a health hazard, all manual handling of surplus blood should be avoided. More or less complicated and, thus, expensive devices having water curtains and exhaust means have been suggested, see e.g. U.S. Pat. No. 4,106,828, to handle surplus blood in the spinner.
U.S. Pat. No. 5,326,398 discloses the arrangement of the slide in a separate plastic case during the spinning operation. The case has small apertures through which blood can be dripped onto the slide, and the case encloses the major part of the slide such that blood that is moved away from the slide is caught in the case. Before and after spinning, the slide is, however, handled manually and without the case.
U.S. Pat. No. 4,197,329 discloses a blood spinner, in which a slide is placed in a recess in a rotatable part. A waste-receiving material in the form of e.g. a sponge is placed around the recess in the rotatable part. During spinning, waste blood is received in the waste-receiving material. Before and after spinning, however, the slide is handled manually in a traditional way. U.S. Pat. No. 4,108,109 discloses a similar spinner.
It is becoming more and more common to carry out differential calculus by means of a flow cell apparatus which automatically analyses the blood in liquid state. In contrast to the above-mentioned methods, the sample is, however, consumed after the analysis in the flow cell apparatus. This means that it is not possible to make a manual second check under microscope if the samples need further checking, which together with the high price of the flow cell apparatus is a considerable drawback of this method. Thus, there is a need of methods for differential calculus that are based on the use of slides which permit both manual and automatic analysis of the sample.
The above optical methods for differential calculus are all based on the use of slides with a varying degree of manual handling. As is well known, a slide is a rectangular plate of glass or plastic, which has two plane-parallel major faces, a sample which is to be analyzed being placed on one major face. However, slides are difficult to handle. They are difficult to pick up, hold and store. They are relatively fragile and may cause wounds in the form of cuts. If the samples that are to be placed on the slides consist of blood or the like which may transmit an infection, the handling thereof involves a health hazard as well.
U.S. Pat. No. 5,225,266 discloses a device, which comprises a rectangular slide surrounded by a rectangular plastic frame. At one short side of the slide, the width of the frame is greater, thereby forming a grip portion. The thickness of the frame is approximately the same as that of the slide.
Moreover, U.S. Pat. No. 4,159,875 discloses a device comprising a rectangular, substantially flat slide holder, one side of which is arranged to support a slide. The holder is designed to protect the slide from being scratched during transport and to permit stacking of slides and alignment of slides in automatic handling.
None of these two prior-art testing devices, however, solves the problem of taking care of surplus testing and/or additive material. Thus, none of them can be used to handle blood or the like in a safe manner.
In view of the above, an object of the invention is to provide a device of the type described by way of introduction, by means of which blood and other specimens can be handled in a safer manner than in the prior-art devices.
This object is achieved by a device according to claim 1. Preferred embodiments are stated in the subclaims.
The new device is in the form of a dish, of which the plate-shaped portion essentially constitutes the bottom. A string of an absorbing material is arranged in a loop along the circumference of the plate-shaped portion. The absorbing material serves to absorb surplus specimen liquid and additive liquid from the specimen-receiving surface of the plate-shaped portion, which reduces the risk that the user comes into contact with the actual specimen. The string of absorbing material is preferably, but not necessarily, arranged in direct contact with the circumference of the plate-shaped portion. The absorbing material further serves a particularly important purpose when the device is used for blood that is spun. By the absorbing material being arranged along the circumference of the plate-shaped portion, the sharp edge at which the blood is normally aerosolized during spinning is in fact eliminated.
Since the absorbing material is part of the device, it is besides obvious that the device has been used, and therefore it cannot be reused by mistake.
The device thus is dish-shaped, which means that it is easy to grasp and that the risk that specimen substance escapes the device is very small, which is advantageous when, for instance, blood is to be transferred directly from the pad of the finger to the specimen-receiving surface.
The frame protects the user from direct contact with the absorbing material. In one embodiment, the string of the absorbing material essentially forms the frame of the device, the outside of the frame being fitted with a protective barrier which prevents absorbed liquid from escaping through the frame.
The frame engages the plate-shaped portion such that the device forms a coherent unit. In one embodiment, the frame and the plate-shaped portion are made in one piece.
The plate-shaped portion is translucent such that optical analysis can be carried out by means of light that is transmitted through the specimen on the specimen-receiving surface. Within the scope of this, the plate-shaped portion could be provided with a reflective layer on the underside such that light can be reflected back through the specimen in the optical analysis.
The inventive device can be used for all types of specimens that are to be smeared on a surface and analyzed optically, but it is particularly advantageous for blood samples.